1. Field of the Invention
The present invention relates to a display device. More particularly, the invention relates to a liquid crystal display device that ensures the reliability of its seal portion when serving as a narrow frame display device.
2. Description of the Related Art
Liquid crystal display devices are generally configured to have a thin-film transistor (TFT) substrate disposed opposite to a counter substrate with liquid crystal sandwiched therebetween, the TFT substrate typically having pixel electrodes and TFTs formed thereon in a matrix pattern. The display device forms an image by suitably controlling the light transmission factor of liquid crystal molecules for each pixel.
There is a strong need for medium-sized and small-sized liquid crystal display panels to maximize their display area while keeping their external shape small. This requires reducing the width between the edge of the display area and that of the liquid crystal display panel, thereby constituting what is known as a narrow frame display panel. The narrow frame display panel is characterized by a narrowed sealing width of the sealant that bonds the TFT substrate and the counter substrate together. This structure can entail problems with the adhesive strength of the seal portion.
Alignment films for initially orienting the liquid crystal are formed on those surfaces of the TFT substrate and the counter substrate which come into contact with the liquid crystal. Heretofore, the alignment films have not been formed over the seal portion so as to improve the reliability of its adhesive strength. However, narrow frame display devices make it difficult to keep the alignment films off the seal portion. To consider the reliability of the seal portion in terms of adhesive strength thus requires studying the adhesive strength between the sealant and the alignment films as well as the adhesive strength between the alignment films and their base films.
Japanese Unexamined Patent Application Publication No. 2012-189856 discloses a structure in which indium tin oxide (ITO) is disposed on wire-formed concave portions of the display area so that the alignment films over the concaves will not be rubbed off. The structure is intended to improve the adhesive strength of the alignment films. Japanese Unexamined Patent Application Publication No. Hei 10(1998)-206871 discloses a structure in which ITO-formed wires are passed under the seal portion to extend over the terminal area. The disclosure does not mention where the alignment films are to be applied.